The esterification of lauric and stearic adds, tall oil fatty acid, and a commercial oleic acid with methanol was investigated using an acid-activated standard montmorillonite (AASM) as a catalyst. Reaction variables such as the methanol :fatty acid molar ratio, catalyst content, and temperature were evaluated. Comparative reactions were performed with K10 catalyst, and similar or even better results were obtained with AASM, indicating that this could be employed as a suitable Lewis/Bronsted esterification catalyst. The experimental results obtained for the esterification of lauric add with methanol were compared to a thermodynamic model. For this purpose, the UNIFAC model was used for the activity coefficient calculation for components in the nonideal mixture. This model has shown that the catalytic system was able to drive the reaction to equilibrium within 2 h, and this was confirmed by comparing the experimental results with thermodynamic predictions.